1. Field of the Invention
The present invention relates to a device for partially shearing thin, flat, hard material with opposing blades having zero clearance. More particularly, the invention relates to a device for cutting the material inward from both sides to leave an inner uncut portion of material.
2. Description of the Prior Art
In the manufacture of electrical power transformers, it is necessary to cut a large number of thin sheets of transformer laminations from a sheet or from a roll supply of, for example, amorphous steel transformer core material. Such cut laminations, which may be about 0.001 inch thick, are then stacked to form a transformer core.
There are many known devices for shearing such thin materials inwardly from an edge of the material. It is also known to use devices which cut material from both sides. Thus, U.S. Pat. Nos. 3,901,116 and 4,619,166 disclose double-bladed saws which advance inward from both sides to cut the material.
However, the above-mentioned devices completely cut the material from edge to edge, failing to leave an inner uncut portion. In modern processing, it is desirable to treat an entire sheet of material at once and, upon completion of processing, to separate the sheet into more manageable lengths for shipping or further processing.
The present invention provides an apparatus and method for partially shearing an entire sheet of material but leaving uncut tab portions which, upon completion of material processing, may be easily broken to separate the sheet into discrete lengths.